Laboratory heating & Ventilation system
VAV ventilation control system /VAV SYSTEM
Airflow control is the control core of the entire laboratory. For the laboratory, in order to fully ensure that pollution cannot leak from the contaminated area of the laboratory to the clean area or even the surrounding environment, to ensure the safety of the outdoor environment and the safety of experimental operators, it is necessary to establish a stable and reliable airflow organization and ensure laboratory airflow. Stable negative pressure gradient. So as to establish a safe, reliable and effective protective barrier.
The variable air volume ventilation system adopts the duct static pressure control method, which is complicated in control and debugging, and is suitable for laboratory projects with large ventilation volume and large number of fume hoods. Install a duct pressure sensor at 1/3 of the system fan and the last branch duct . Used to detect the wind pressure value in the pipeline. The opening of the electric damper of the exhaust equipment in the laboratory area makes the actual pressure detected at the top pressure sensor less than the set pressure value. The control system increases the starting frequency of the roof fan through the frequency converter, and maintains the pressure at the pressure sensor as the set value. When an emergency occurs, turn on the emergency exhaust mode.
Butterfly Valve VAV Control
1) The surface wind speed control system continuously monitors the actual surface wind speed state. When any factor affects the surface wind speed change, the system will automatically adjust the electric air valve on the pipeline to the constant set surface wind speed value. The variable air volume butterfly valve adopts high-quality brand products, has rapid response ability, high air tightness without whistling, high anti-corrosion, fire prevention and many other characteristics. Direct-molded one-piece molding ensures high strength and durability, with a water collecting ring to prevent the backflow of condensed water from the pipeline into the cabinet:
l The valve body is made of PP molded one piece and highly anti-corrosion. It is specially designed for the exhaust air of laboratory fume hoods, and is resistant to various organic / inorganic vapor corrosion;
l Actuator drive mode: full stroke of high-speed electric actuator ≤ 2.5 seconds, using original imported brand actuator;
l The actuator control module has its own feedback microprocessor to achieve high stability;
l The connection between the shaft and the valve body adopts low damping material self-lubricating connection to minimize the resistance of the actuator;
l In order to improve the stronger anti-corrosion ability, no metal parts are allowed in the part in contact with the exhaust gas;
l The shaft and butterfly blade are designed by PP molding to ensure high corrosion resistance;
l Meet laboratory fire protection requirements;
l It has a sealing ring with excellent performance to ensure high air tightness and aging resistance;
l Controlled by the fume hood monitor, the surface wind speed control accuracy: ± 10% of the current surface wind speed setting value ;
l Noise: less than 55dB;
l Operating pressure 50-1000Pa , operating temperature -18-55 ℃;
2) Different parameters can be set on the panel under different experimental conditions.
3) The system realizes that the surface wind speed is controlled at a certain set value (such as 0.5m/s) when there is an operator in front of the fume hood through the infrared monitor. When no one operates in front of the fume hood, the system automatically switches to another setting. Fixed value (such as 0.3m/s) to save operating costs.
4) When the fume hood door is closed, the air volume valve should maintain the minimum exhaust air volume of the fume hood, 300CMH for a 1500MM fume hood .
5) There is a sound alarm when the fume hood door is too high.
6) There will be sound and light alarm when the wind speed on the fault surface is too high or too low.
7) When an abnormal situation occurs, turn on the emergency discharge mode control, and the system will open all the air valves. The maximum air volume of this fume hood is not controlled by the surface wind speed value.
Venturi valve VAV control
During the operation of the fume hood, the most important factor that affects the wind speed on the surface of the fume hood is the pipe network pressure of the ventilation system. Due to the opening and closing of other fume hoods or ventilation equipment, or changes in other aspects of the pipe network, the pipe pressure of the fume hood will change. Such changes are frequent.
If the fume hood system uses ordinary butterfly valves, the surface wind speed of the fume hood will change frequently, which is very detrimental to the safety of the laboratory. Even if the wind speed control system is used, it will only be adjusted after the surface wind speed changes. It will go through a series of sensing, calculation, adjustment, and oscillation processes, and at this time, the unsafe situation has occurred, because the pressure change of the pipe network may occur at any time, and relying solely on the wind speed control system will cause the surface wind speed to be controlled slowly and frequently.
The fume hood control system using the venturi valve can solve the problem of the pressure change of the system pipe network, and the venturi valve can be automatically adjusted according to the pressure change of the pipe network. This process occurs at the same time with the change of the pipe network pressure, thus avoiding the need to adjust the process by the wind speed control system and realizing fast and stable air volume control. It has two different working modes, namely variable air volume and constant air volume.
Variable air volume means that the valve can respond quickly through signals, and the automatic pressure balance device of the ventilation system can respond quickly (response time < 1 second), thus meeting the VAV variable air volume requirements. Constant air volume means that the valve can set an air volume value, so that the air volume inside the pipeline passing through the valve is constant, the control is accurate (± 5% ), and the adjustable rate is high ( 20:1 ).
The working principle of the fan speed control system of the fume hood
l The surface wind speed control system continuously monitors the actual exhaust air volume of the fume hood, and calculates the average surface wind speed of the opening area of the window according to the height of the window. When the pressure of the exhaust duct changes or the height of the window changes, the system responds within ≤ 1S , adjust the opening of the air valve in time to keep the average surface wind speed of the window opening area stable.
l Different parameters can be set on the panel under different experimental conditions.
l The system controls the surface wind speed to a certain set value ( 0.5m/s ) through the infrared monitor when there is an operator working in front of the fume hood . When no one is operating in front of the fume hood, the system automatically switches to another set value ( Such as 0.3m/s) to save operating costs.
l When the fume hood door is connected, the air volume valve must maintain the minimum exhaust air volume of the fume hood, and the 1500MM fume hood is 300CMH.
l When the wind speed on the fault surface is too high or too low, there will be an audible and visual alarm.
l When the temperature of the fume hood is too high, there will be an audible and visual alarm.
l When the door of the fume hood is too high, there will be an audible and visual alarm.
l When an abnormal situation occurs, turn on the emergency discharge mode control, the system will open all the air valves, and the maximum air volume of this fume hood is not controlled by the surface air speed value.
The laboratory variable air volume system and fume hood variable air volume control system we provide all adopt advanced VAV solutions , and strictly monitor and control the laboratory air supply and exhaust , and the surface wind speed of the fume hood through digital controllers.
It ensures that no matter what the opening of the adjustment window is, the inlet air velocity of the fume hood can always be accurately controlled by 0.5m/s , and the change of the air volume of the discharge valve and the air supply valve can be tracked at the same time. Increase or decrease the exhaust air volume to ensure the designed infiltration air volume is constant, so as to ensure the slight negative pressure in the laboratory and the correct airflow direction. The system has strong adaptability and can reduce energy consumption under the premise of fully guaranteeing safety.
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